Toadflax

Yellow Toadflax (Linaria vulgaris Mill.)

Roots: This perennial plant has extensive creeping roots.

Stems: The stems range from 20 to 80 cm (eight to 31 in.) in height and are green, hairless, and un-branched.

Leaves: They are covered with numerous hairless, virtually stalkless leaves 2.5 to seven cm (one to three in.) long, six mm (1/4 in.) wide with the narrow part of the leaf at the base. New shoots produced in clumps are found narrowly spaced along the lateral creeping roots giving the plant a bushy appearance.

(Note: A broadleaved species, dalmatian toadflax (Linaria dalmatica), is also found in Saskatchewan but is not common, being associated mainly with abandoned yard sites.)

Flowers: Yellow toadflax flowers are shaped like a snapdragon, have a long spur that points backwards and are half the length of the flower. Flower colour is mainly butter yellow with the petal tips of the petals more orange. Flowering occurs from June to October.

Seeds: Seeds are flat, somewhat circular in shape, warty in texture, brown/black, very small and broadwinged. One yellow toadflax stem is capable of producing 5,000 seeds. Unlike leafy spurge, yellow toadflax does not contain milky sap.

Reproduction

Creeping roots and seeds.

Historical use

When first introduced to North America, toadflax was grown for ornamental and medicinal purposes. However, the weedy potential of the plant was soon recognized.

Yellow toadflax was commonly used in folk medicine and homeopathy. In the Middle Ages it was specifically used to:

• Treat throat ailments, especially scrofula or tuberculosis of the neck, causing enlargement of the lymph glands of the neck, a very feared disease of those times.
• Heal ulcers,
• Carry away the water of dropsy, (edema or swelling from water accumulation) and
• Remove liver and spleen obstructions.

When combining yellow toadflax with lupin powder, citizens of the 16th century believed they were healing scurf, leprosy, skin spots and pimples, wheals and morphea. Extracts with water were thought to remedy the heat, eye inflammation and redness.

Chopping up the whole herb plant and combining it with grease from an old hog was thought to cure piles, ugly sores and other skin eruptions.

The 16th century people also believed toadflax to have mystic powers especially when combined with the number three. Stringing three toadflax seeds on a linen thread was thought to be so potent it would protect the wearer from all evil. An evil spell cast upon you could be broken simply by walking around a yellow toadflax plant three times.

In more modern times, budding plants have been used for astringents, and treatments of jaundice, liver troubles and various skin diseases.

Yellow toadflax was made into a lotion to treat insect bites. This practice was done in both England and New England. Other uses were as fly repellents over doors before the days of screens and flypaper.

Settlers would boil yellow toadflax plants in milk and pour the liquid into saucers to poison flies.

Toadflax was a major source of yellow dye. This would have been its most common use. Once chemical dyes came on the market, this use was discontinued.

Location

This escaped ornamental has naturalized throughout North America. It is a very destructive weed found along roads, railways, rangeland, forage stands, pastures, mountain meadows, disturbed soils, waste areas and cultivated land.

Concerns

Toadflax has toxic chemical compounds poisonous to cattle. Usually cattle dislike both its taste and odour, so poisonings from grazing are rare.

Hay with a high toadflax content has the potential to cause poisoning, as cattle have more difficulty avoiding the plant in hay. Agriculturally, this plant is a menace because it is a prolific seed producer. The seeds can survive in the soil for up to three years. They can be transported by water, wind, machinery, feed, birds and animals.

Creeping rootstocks of yellow toadflax can increase radially up to two m (six ft.) if left in untilled summerfallow. This feature, together with its prolific seed production, enables it to rapidly invade over-utilized areas.

Control

In crops, thorough cultivation helps to control toadflax to the point where next year's yields will not be reduced. Yellow toadflax can be a problem in low disturbance direct seeded fields.

Crop tillage can hold toadflax in check. This works most effectively in summerfallow where cultivation is done when flowering commences. When new growth is observed, be sure to cultivate again within eight to ten days or when new shoots reach 10 cm (four in.). Note: This will promote the germination of viable toadflax seeds found in the soil. Broken root pieces will send up new stalks also. With continued summerfallow, both new plant sources should be eliminated. Take care to clean tillage equipment when moving to another field to avoid furthering the infestation. (Caution: excessive tillage could cause soil erosion.)

Pre-harvest glyphosate can be used to control yellow toadflax when terminating hay grain or in crops where the practice is registered.

It has been observed that crested wheatgrass will check the spread of yellow toadflax but never eradicate it totally. Use the crested wheatgrass for hay, pasture and forage stands. A healthy stand is important so it can compete with the weed.

Mowing to prevent seed production is a useful tool.

Research on biological control using insects is ongoing, with limited results to date. Large toadflax infestations have been reduced considerably by flower feeding beetles in the 1950s. Some areas in northwestern Saskatchewan still experience large toadflax populations.
For very small patches of toadflax, hand pulling every three to four weeks beginning in June will help control but not eliminate the plants.

In rangeland, chemical control is practical. Spot treatments with Tordon 22K has worked effectively (95 per cent control). This chemical can be used throughout the growing season, but patches are more visible and thus easily treated if applied at the flowering stage. Note: The active ingredient in Tordon 22K is picloram, which does not readily break down. It may persist for more than five years. It also is soluble in water, moving easily through the soil to the water table. Therefore, it is not a chemical to be used on coarse sandy soils. Often, it is the sandy soils where large toadflax populations persist. Applicators should apply herbicides at least ten feet beyond the visible patch to control plants emerging from seed.